The use of flow-controlled lubricant pumps in combustion engines in order to be able to bring for example a delivery rate and a pressure up close to the respective requirements of the combustion engine is the state of the art. In most cases, this is performed by way of the loading of an actuating unit within the lubricant pump, such as for example a control piston or an adjusting ring, with an oil pressure originating from a main oil gallery of the combustion engine. The disadvantage of such a control lies in that the control is directly connected to the oil pressure prevailing in the combustion engine, the flow rate, an engine rotational speed, a lubricant temperature and a spring force applied to the actuating unit. The objective of so-called characteristic map controls is the decoupling of the mentioned direct influence quantities on the control in order to achieve a control characteristic map of the lubricant pump, which can react to each individual influence quantity so as to come closer to the requirements of the combustion engine and at least reduce further drive outputs and dissipations. To this end, proportional valves are mostly used which switch a control oil pressure from the main oil gallery or from an output of the lubricant pump to the actuating units on or off as required.
If instances of controlling occur in such a control circuit or a defect of the proportional valve occurs, this can lead to an undersupply of the combustion engine and thus a damage of the latter. For this reason, a type of emergency operation control at a higher pressure level is provided with the usual lubricant pumps in order to continue supplying the combustion engine with lubricant even in the event of a failure of the proportional valve. Such a so-called “second level valve” constituting a type of piston valve is loaded with lubricant pressure on both sides in normal operation and on one side preloaded with a spring in order to be able to hold the actuating unit in a preferred position so that the control pressure from the proportional valve can directly act on the actuating unit of the lubricant pump. In the event of a defect of the proportional valve the lubricant pump does not receive a cut-off pressure via the proportional valve and thus delivers the maximum possible rate of delivery into the main oil gallery of the combustion engine. The second level valve in this case is loaded with the rising lubricant pressure of the main oil gallery only on one side and simultaneously assumes a position in which the lubricant, i.e. the oil of the main oil gallery can flow into and out of the actuating unit as a function of the oil pressure, thus regulating the lubricant pump to a desired higher pressure level. Disadvantageous with such a lubricant supply system however is a high parts variety with concomitant high assembly, storage and logistic costs.